It's the opposite for me mostly. That is what makes the Winchester Curse(if you befriend them you'll most probably end up dying some horrible death) so bad. Sam and Dean are just two people, it's the various guest characters that add a lot to the show. But they tend to take on the lifespan of a mayfly when they befriend the Winchesters. It's not even just people they befriend, but even if you're some random person that got saved by them...even that brief association might get you killed(As Crowley did to many of the people they first saved).
There are a few exceptions. Poor Bobby avoided it for years, but eventually it got to him and he didn't just get killed they ruined his afterlife as well. With Bobby gone it seems Sheriff Judy is now the longest surviving ally. Can she avoid the curse indefinitely? Who knows.
For all the talk from Sam and Dean about how being a hunter is always going to end badly and bloody..they sure do cheat death a lot. Death itself wasn't even able to cheat death in the end lol, but Sam and Dean just keep going and going. Why doesn't God just make them these immortal hunters and get it over with? When Sam and Dean die the Earth is most likely going to end within a few decades at most.